The watch is powered by the Longines caliber 507.2, a https://www.pnhwx.co.uk/Collection/submersible/ hand-wound movement based on the ETA 6498/2 with a 53-hour power reserve. https://www.rmwx.co.uk/Collection/rm-53/ When it comes to size, the Heritage 1938 doesn't follow the same script as the original. It's sized up for modern taste at 43mm as opposed to the typical 32 to 36mm watches of the https://www.iwcx.co.uk/Collection/ingenieur/ WWII era.